I am using Manger drivers for more than a decade and still find their basic sound quality fascinating. But they are not perfect: dispersion of HF, notch in frequency response at around 800 and 1600 Hz and high distortions at that frequency range. Manger developed new speakers but there is no upgrade of the driver itself for more than 2 decades.
I found Moongel .: RTOM Corporation :. which is used for damping drums and thought to try it on the MSW as they are quite cheap. No effect when used in the periphery of the outside or in the center of inside. But there was some positive effect when the moon gel was applied at the center of the MSW on the frequency response and much more significantly on the distortions levels of the midrange. (filtered at 400HZ)
yellow: MSW alone
dark violet: MSW + Moongel at center

I want to make a test build on two 8'' woofers I have, one I'll build normally, paper cone and dustcap (epoxy glue on the junctions), and the other I'll build with an additional paper whizzer cone to see how they do in the mid-ranges (in terms of on-axis sensitivity mostly, quality isn't my main goal).

But I'm wondering: should I use a more flexible material to bind the voice coil with the main cone, so as to decouple it more at higher frequencies, and use epoxy to bind the whizzer cone to it?

The glue I have for this is this one below, it looks like acetic silicone sealant, but it isn't, it's a transparent hybrid adhesive that's at least some 6x stiffer when dried, and it's much, much stronger in binding to surfaces too (you can't peel it easily like you can peel silicone sealant).

However, I'm wondering if it's necessary. Does the flexibility of the main cone itself already do the trick? Or is a more flexible glue required to decouple it better at higher frequencies?

New in box. Well, old, but unused in box. Project never went anywhere. $100 including shipping in CONUS.

Jon

or worst. Please let me know which ones to look for and avoid. Thank you

I have an electronics problem I thought you might be able to help with. I have attached a bit of the schematic to a Fender Rumble 30 bass guitar amplifier. I believe the power transformer has failed. The problem is Fender has declared the parts for the amplifier obsolete and I've scoured the planet for spare parts suppliers, without success. I don't have enough knowledge of transformers to be able to identify a suitable substitute. I have looked at element14 and RS-Components, but really don't know what I am looking for.

The primary input is 220-240VAC protected by a 0.5A fuse. The secondary is centre tapped to give 25.7VAC and phase-inverted 25.7VAC. I don't know if these are rms values. The dimensions are 70x70x60mm.

Are these specifications enough to identify a suitable replacement transformer?

Any ideas?

I like HT and 2-ch systems. I build relatively modest speakers compared to some here. I enjoy designing x-overs. Sims are fun. I'm old school, and do most of my x-overs by trial and error, but with measurements instead of software. I've been at this for quite a while. I'm hoping to assist others with their x-overs. I may build some new mains soon using Peerless drivers.

Hello,

Does anyone have two LM4780 they'd be willing to part with?

I have finally got around to building the two PA03 that I bought 10 years ago!

Regards,
Matt

SSTART Pcb and power supply project - CNC Routing

Hi all,
I've recently finished building a small CNC router, and intend to use it to mill pcbs. There is of course quite a few steps in between knowing it can be done and achieving the goal, so this thread is intended to explore the process of learning to use the thing and producing some pcbs that I can actually use. As such I thought I'd pick something relatively simple to build and work through all the steps along the way. I should emphasize that I'm a learner at all of these things so this will serve as a documentation of my mistakes along the way I suspect... 🙂

The planned project - the SSTART Preamp and a as yet to be determined power supply - I'm thinking something based on the psu described in the BOSOZ though at the moment
The SSTART Preamplifier Why on earth would anyone do such a thing? Article By Grey Rollins
http://www.firstwatt.com/pdf/art_bosoz.pdf

I intend to design a stereo pcb in eagle, then use
Welcome to PCBGCODE to generate the Gcode

the cnc router is a Shapeoko with a few little mods
Shapeoko | Precision by DefaultShapeoko | Precision by Default

using mach3 to drive the CNC router
ArtSoft USA - Home of Mach3 and LazyCam

And possibly using Mastercam to refine the Gcode
Mastercam CAD/CAM software

I'll do my best to detail what I accomplish along the way and we'll see how it goes.

Music to work to today - Cake - Comfort Eagle

Looking for Amperite 6NO30 delay relay, possibly 6NO15 or 6NO25 as alternative.
8-pin octal socket.

Regards, Gerrit

I'd like to preface this with a disclaimer that I am relatively new to this and this is my first scratch build after building a number of kits and lower stakes scratch builds (passive preamps, etc.).

I've just finished putting together Nobu Shishido's Loftin White inspired amp and I've attached a schematic below and you can see in blue, that I've made a few small changes to the circuit. The changes were made to reflect parts I have on hand as well as some small safety tweaks. The power supply was modeled - to the best of my ability - in PSUD and seemed to be within spec. Changes below...

1. The power transformer that I have supplies 420V AC instead of 400V AC.
2. Replaced the 5AR4 with a 5U4GB (for more voltage drop to account for the different power transformer).
3. Replaced the first 100uF capacitor with a smaller 20uF capacitor after the rectifier tube.
4. Added a 100uF filter cap in parallel with the existing 100uF filter cap.
5. Added a bleeder resistor.
6. There are diodes on the 5U4GB a la the Dynamo rectifier mod I've seen online.
7. There is also a NTC thermistor on the 120V AC line

The build is done and I'm slowly working through starting it up and measuring voltages etc. I've powered it up with a dim bulb tester and no sparks etc. and the AC filament and high voltages are good.

I then powered it with a dim bulb tester with just the 5U4GB rectifier. Again, no sparks, etc.

When I power it up without the dim bulb tester with the rectifier and just the 12AX7 driver tubes, I am getting 518V B+ at the first power supply cap and further along only 4V B+ going to the preamp tubes where I should be seeing 300V. These are marked in red on the schematic.

I am still working to understand aspects of the schematic but my questions are as follows:

How much will the 2A3 power tubes drop the B+ once there is more load on the power supply? I ask because I don't want to destroy the tubes.

Is there an explanation for the extremely low B+ voltage at the last preamp filter cap? The driver and power tubes are inextricably linked in these circuits but can't wrap my head around the 2A3s effect on this measurement point.

Thanks in advance!

I have two genuine built by Nelson Pass B1 pre-amps. Both have had mild use, look new. $175 each including shipping in CONUS. Neither has a power cord, but they are easily purchased at your local hardware store if you don’t have one at home already.

Jon

Hey everyone!

Little teaser intro - I changed the response of my Seas coax tweeter from the Red trace to the Green trace (not actual level, separated for clarity).



In 2022 I purchased the Seas MR18rex/rf which is a coaxial mid-range and tweeter. Sadly, I was disappointed by the performance of the tweeter. The on-axis response is horrible and you need to go a decent way off-axis before it smooths out. The on axis response is what you see in the red trace above. Rutcho found similar results*



So, I decided to have a go at making my own tweeter for it.



There are a limited number of tweeters small enough to fit inside the voice coil of the mid-woofer and I tried quite a few. I settled on the OX20SC00. It doesn’t fit as standard because its too deep and also unstable on the pole piece. Luckily I have a cnc milling machine, so I made a jig to hold the tweeter safely and modified the body.

I then took a casting of a section of the mid-woofer cone and carefully modelled the profile in CAD. This allowed me to draw up nine variations on interface parts between the tweeter dome and the cone. I 3D printed all nine and yesterday I tested each one in my anechoic chamber. One or two worked surprisingly well! big smiley face

The response is below. Traces top to bottom with 5dB separation:

0 degrees (absolutely dead on-axis)
5 degrees
30 degrees
60 degrees



Additionally, below is the distortion at ~90 dB* I applied a 1st order DSP filter at 4000Hz which produces an almost perfectly flat frequency response from 1KHz up.



As typical for large roll surround tweeters 2nd harmonic is slightly raised, but >3rd harmonic is very low. For a small tweeter, this thing could cross low when used in a waveguide like this. It brings to mind the Buchardt S400 with their 19mm dome in a 6” waveguide.

I’ve looked at all the coax drivers on the DIY market and this seems to be the best tweeter performance of any of them. Seas original, SB Acoustics, Tangband all have some nasty diffraction and dips going on in their tweeter response. The mid-range cone from Seas is excellent, of course, since that is their area of expertise.

So here is my question – If you are in to coaxials, would you be interested in this tweeter upgrade as a product? I was thinking about selling the modified tweeter and waveguide piece as a plug and play kit for the Seas MR18REX/RF. It would probably be about $50/piece.

If there is interest, I also considered talking to a distributor like Sound Imports. Seas told me they can sell the MR18 coaxial without the tweeter for a lower price but there is a prohibitive MOQ for someone like me. Working with a distributor who already has a relationship with Seas, they might be able to get a tweeter-less MR18 and offer it with my tweeter upgrade at a price similar to the original MR18 giving better value. However, I’d like to gauge interest.


Footnote:

I simulated the design in AKABAK. As can be seen in the measured response the traces bunch up a little between 5KHz-10KHz. This is due to the cone profile of the MR18. I have put some thought in to designing my own coaxial from the ground up so I can do an even better job, but again MOQ and non-refundable costs are prohibitive and scary for one guy like me. At least offering this upgraded MR18 could ‘get my feet wet’ and perhaps the future would hold more exciting things!



SEAS MR18REX/XF H1699-08/06 Loudspeaker Measurements and Information (rutcho.com)
*My SPL meter died. So I had to use my phone to set SPL for distortion measurment)

Hello,I have a problem with the latency of my two 2x4HDs. I use them one in each loudspeaker. The analog input is in use. Every time I start the MiniDSPs, their latency changes. How can something like that happen? I don't change the programming or anything else. Only on/OFF. the microphone stand still at one place. I noticed it because my sum signal from the left and right is always measured differently. In the picture below, i startet the dsp´s for every loopback measurement new.

3 times left and three times right on/off, 6 different latency´s

4 stereo measurments 4 frequency responce


greetings Marius

I'm a guy who likes to enjoy good music with acceptable quality, studying degree in computer networking, and through this space I intend to learn more about how small and powerful class D amplifiers work.

Hi Guys

I am building my firs set of desktop speakers and am currently designing the crossover.
I am trying to cross the Dayton Audio DSA135-8 5" & ND25FW-4 1".

From what I have learned the right place to cross these, is around 3000Hz.
This is the schematic I came up with after following the basic Guide by AllenB and tweaking it a bit.

What do you guys think? Is this a usable crossover?
Also I might want to change the tweeter for the Peerless by Tymphany BC25SC08-04 for aesthetic reasons.

I have attached the spec sheets for reference below.

Would love some feedback!

Thanks

Sam


Response Simulation Dayton Tweeter




Peerless Tweeter

I recently bought a 2nd hand Hypex HS200 with a Shiva III to build a subwoofer (http://matthew.augier.info/index.php?album=/DIY/STS_II) from a guy who I trust to be honest. Got to the stage today where I wanted to test, connected it all-together and nothing. Everything is connected as it should be (green euroblock + to shiva+>+ and same with - side. But not a bean out of it. When the panel powers on in standby mode the light is yellow, and when sub sounds cut in it goes green as expected. So I tried another driver (8-ohm direct connect bsb-12) still nothing, which makes me think something is wrong.

My connection is only mono and the panel has stereo in, I tried left/right which made no difference, does it need a y-adapter?

Something else wrong? Any advice welcome, I want to get this baby rocking (yes it's a svs clone, and I'm just waiting for the to grill)

I bought 12 pairs from group buy for my amplifier. But after some testing with normal vishay ones, it seems that my amplifier topology (HEC) does not require the Harris ones. So I will let those pieces go at cost, preferly in EU since the import custom has been paid.

MELF metal film is better than other SMD resistors?
A simple question for those who have more experience in audio projects.

Who can upload the schematic diagram from the plate amplifier (PCP-No E162886) of this model ?
Identical with Rythmik Audio Subwoofer Amp.

The driver comes from ISO acoustics (Model 13BH-10024SA)
Contact Us About Our Ultimate Speaker Stands

History of Leema - go to
Leema Acoustics – Alex Giese GmbH
Currently there are products in other kind available:
Leema Electro Acoustics
first time online 2002:
Wayback Machine

Phono LCR preamplifier

Designed by Sakuma, built entirely with Tamura transformers.

Has the ability to adjust the RIAA curve in 3 settings, according to the source material or taste of the user.

Separate signal and power supply chassis

6SL7 on the input, 6SN7 transformer coupled on the output, tubes are DC powered

Power supply has AZ1 as a rectifier and about 200H of induction, for a quiet power supply

If you have any questions, feel free to ask!

SOLD

More Weird ideas!

Trying to combat the evil of rear cabinet reflection without the obvious solution-fiberglass or sheep wool.

Will it work? what do you think will happend?

Hello,

I am new to speaker building, being 30+ years a pro musician I have DIY as a hobby. I am looking for exchaning ideas and learning new stuff here. Very excited to be here.

Thank you and enjoy your weekend

Upgrading Vacuum State FVP FVP-5 Tube Line Stage to FVP-6

Please note, the FVP-6A and FVP-6B line stage schematics are (C) Copyright Joe Rasmussen & Vacuum State and only single user license is granted.

The original FVP5 schematics also had shared copyright, but SVP-1 and SVP-2 are Copyright Vacuum State. Their schematics have similarities but will not be shown here as I consider them belong to Vacuum State which will still make them. So understandably, I am not comfortable in posting them.

Here for DIY purposes, we shall show two variations called FVP-6A and FVP-6B:

What makes them new is that they are based on the 12AT7A/ECC81 tube instead of 6DJ8/6922/ECC88 tube. Down here in Australia a number of FVP users were persuaded on my recommendation to change away from the ECC88 tube to the greatly underrated "T7" tube in the line stage (the ECC88 remained the same in the phono stage). Nobody regretted it and reported they liked what they heard. There is something about the "T7" tube, it does not try to be high or low gain or mu or anything special. It seems to hit a sweet spot of its own. Like it is not trying to do anything hard.

OUR PROBLEM? CONTROLLING THE GAIN!

This what the early FVP5 did to control the gain, a resistor was added to draw additional current and it looked like this:



This is a crude way of lowering the gain to something manageable. In effect the 25K and 47K look in parallel and also brings the Anode voltage down to where we need it to be. BUT...we want to avoid using this resistor and there are two ways of doing it as well as being able to set the gain where we want it.

The two methods both involve using a current sources.

The reason for being two variations, FVP-6A and FVP-6B, it has to to with FVP-6A requiring an added negative voltage (-15V), and FVP-6B does not.

Both methods should work well. The "B" variant is simpler as it does not need an added negative power supply.

The schematics as shown uses +250V, but it could be used with as low as +210V, but with lower voltage the circuit adjustments in the circuit become more critical.

Gain is aimed to be around 15dB approx (5-6x) but it can be trimmed a bit lower. For sure these things can be discussed as we go along. We gain discuss what is needed to do to get the gain you want. How that can be done, this we can discuss as we go along.

Here is the FVP-6A schematic:




Some simple modeling:



(100mV in and 560mV out.)

What you use as a current source is up to you. Dial in enough current to get you approximately +130V on the Anode of the input gain tube. This also provides a good bias voltage for the buffer stage "Super Linear Cathode Follower" or SLCF for short. This is the key voltage in the circuit.

How you get the +250V is up to you. You can use a SuperReg for sure, but whatever you use, note that it will have an effect on the result, the sound. Power supplies always does.

The +15V comes from the filament supply. The "T7" filaments are wired in +12.6V (series) and are fed with an inline 15 Ohm 1W resistor with will drop down the voltage by a couple of volts. This also creates a slower start when the filaments are cold and good for long-term life.

The -15V needs to be a dedicated supply and it to needs to be regulated. The R9 resistor value "???" is adjusted, so that +130V appears on the Anode of the "T7" gain stage. The R9 value here should not be copied, the correct value needs to be found.

Some may have noted that the SLCF uses a Darlington instead of a HexFet IRF710 used in the Vacuum State circuit. This is to avoid this 47K resistor:


This resistor should ideally be eliminated. The 47K was required because the HexFet's non-linear capacitance could affect the performance. Allen decided to add enough resistance to prevent it from misbehaving. Of course, the SVP variants used an actual tube and that meant he could get rid of that 47K. But here we don't have that option. Hence the idea was developed to used a Darlington with a gain of 500 or higher. The MPSA29 should do the job nicely, but will need a 33-47V Zener to protect it.

The R4 470K or 560K needs to be adjust so that the voltage drop caused by the Darlington is 15-20V. Hence the Anode of the follower will see around around +230V to +235V.

How you come up with the +250V and -15V respectively, we can have a discussion about that.

Next is the FVP-6B Schematic:



Some simple modeling:



(100mV in and 600mV out, gain = 6)

Now we have done away with the extra negative power supply. That is quite a few components eliminated.

Note: Only four additional components, three resistors and one HexFet, typical an IRF710 or IRF820, per channel.

Note that Anode load value is lower and so it the Cathode resistor value, compared the FVP-6A. In this circuit, it is R11 that is adjusted to give the same +130V.

This current source effectively takes the place of the 47K resistor that we might other wise have used. But a current source presents a hugely larger impedance, indeed the ideal current source is infinite.

The FVP-6B does draw more current from the +250V power supply than the FVP-6A.

Please note re the Buffer or SLCF, it does not have the same output grunt as the ECC88 version. But it is quite adequate for our purposes. We are mainly concerned about the sound.

So there you are. I am sure that there will be lots to discuss, but much of it should be obvious to seasoned DIY'ers and also for them to be helpful to others.

Let the building commence...

Posted them couple of years ago.
Someone was interested a couple of months ago but I couldn't find them in the storage. Here they are

Hi. Software engineer here, working on Qualcomm audio dev kits. Hoping to get some insights from other people who have similar experience as me.

Hi there
I have just got a Krell S150m monoblock on the bench, it has a linear PSU driving a class D amplifier. Does anyone have a schematic for this amp. Either reverse engineered or from Krell themselves.

Anything to get me started would be good.

Fault is distorted output, any ideas greatl;y received

Thanks
Simon

Looking to get someone to develop a device based on QCC51xx with output as USB C [via I2S or other Option] which can be connected via PC. OR if any product is already there, would be happy to get help on those link.

Hi, I need to work on programming the qualcomm QCC5171. I got a code example of bluetooth headset. The first step I need to do is understanding the example. When I open it in Qualcomm's MDE, I am totally lost, though I know C/C++ programming.

Can anyone point me to a programming guide of this chip? Thank you.

I thought I’d fixed my B&O CD3300, type 5142, as I managed to get it to play most of my CDs. I’ve replaced all electrolytic capacitors on the power supply, decoder board and servo board. But, after leaving it for a few days it now plays none of them. In most cases the TOC are read, but it won’t play.

I now want to check the laser power. The service manual says to put a meter across R3102 to check the mv. But, my servo board, number 5886 on the sticker, doesn’t seem to have that resistor.

I’ve attached pictures of both sides of the board and would really be grateful if someone could point me to the resistor. Yes, I know the blue capacitor by the 1K0 variable resistor is missing. I took the picture before I put it back in.



According to this link,
https://www.condoraudio.com/wp-cont...hilips-CD650-CD-Player-Restoration-Repair.pdf

The resistor should be in the top right of my picture showing the solder side, just next to the 14 pin ribbon connector and not far from the 104 resistor. But, my board just has a gap.

These speakers are in factory boxes and new , with spect sheet
just look 99$ and shipping SOLD SOLD
SOLD
thanks Rick

Hello, I'm searching for a high quality TPA3255 output filter inductor as classic, non SMD type.
Wurths 7443631000 and 7443630700 are SMD only as far I can see.

Are there any good alternatives in the 7-10 uH range?

SOLD

Could someone please help me? I'm repairing this Helix A2.

It came with several problems at the source.
Firstly, I would like to know which component is missing and the correct value of the capacitor that was replaced.
Both components are circled in yellow.

Thank you in advance to everyone who can help.

Hey,

my name is Benni and I did some modding of guitar pedals some years back. Two years ago I designed and built two MIDI controllers, which was a lot of work but payed off as I use them in my music quite a bit.

Right now I'm looking for some feedback for a circuit of a phantom powered piezo amp I modified.

Cheers,

Benni

New here and wanted to eventually get my feet wet in building some figure diy dac/amp projects. It's a little intimidating at first but I'll learn. Would also be very interesting in buying some DIY dacs projects other people have completed and looking to get rid of!

I’m excited about having meaningful discussions, exchanging ideas, and expanding my knowledge with the help of this amazing community.

Has anyone done this project:
https://sound-au.com/project63.htm

There are two implementations:
https://sound-au.com/project84.htm
In-out stage:

The bandpass module:


https://sound-au.com/project64.htm
Different layout and mixer:

Corresponding mfb module:


I prefer the second one, where we can have single opamps before and after the mfb modules.

I am trying to simulate both, using the values and the calc tool in the website, but neither the frequencies, nor the cut/ boost gain matches with the values of the elements 🙁

I apologize for doing it this way but I just joined and cannot start a conversation. I need help with my Dual 606:
Might anyone know who the MANUFACTURER is and what the MANUFACTURER's part number is of the TRANSFORMER for the Dual 606?
Is there any chance you have it or know where to find it?
Thx,
-Roy

Hi all, I am sharing the layout of the PSU module of Linn major DSM/4.
Hopefully, it helps someone interested.
This is a class V power supply module.
Figure 1 is the layout in the mainboard.
Figures 2 and 3 are layouts of cables from the power supply unit.

FS a Pair

NERO-6MRN150D SB Audience​

only used for test .a very dynamic midrange

https://www.sbaudience.com/index.php/products/woofers/nero-6mrn150d/


Price 330 euro

For sale a pair of Jensen Trafo JT-11-DMCF

https://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-11-dmcf.pdf

price 107 euro

only sale for EU

So I'm quite liking my Telefunken RE074 neutro DC1938.

The tone is very good, with a more 'colourful' presentation, (not ugly ) than the CX301-A , with slightly more compression ...however it has this Nazi Swaastika printed on the tube.
.
Is it ok to use such a tube?

Hello everyone,

I am a music and audio equipment enthusiast, I enjoy building tube equipment and modifying, repairing, improving audio equipment. I own a modified Teac P700, which transport, using various DACs I built, as well as a Conrad Jhonson Premier Nine, (magnificent devices the Premiers). The transport employs a Sony CXD1125Q DSP, which also has three connections for Sony's “2's complement signal 16bit” format. I would like to be able to take advantage of this output to connect it to one or two AD1865 DACs in NOS configuration. Unfortunately, I cannot find an interface, perhaps even a simple one, to bring the Sony format, 16bit to 18bit, compliant with what is needed for the DACs.

Is anyone aware of or has experienced such logic? Perhaps for 20bit or 24bit DACs to be derived........
I welcome advice and guidance of any kind.

Thanks in advance
ICHINO

CamillaDSP need no introduction and what is it not to love? An Open Source DSP written in Rust by a fellow Swede! I have read about different uses cases like active XO and room correction but why try to use it as a preamp?

My first experience with a DSP was the ADAU1701 based one by 3e Audio. It started out as an active XO but ended up as a preamp. The background and build is documented on my blog. The Linkwitz Transform worked really great with my current speakers but relying on an old laptop with proprietary SigmaStudio and a shady USB-interface for maintenance never feel right. That is why I got quite excited when I discovered CamillaDSP, here was an opportunity to replace proprietary tech with Open Source hardware and software! I just need a proof of concept and that is why I started my latest project - DSPreamp.

The code took me just hours to write but integrating hardware and software into something resembling a preamp took weeks. I have now bench tested everything I set out to do and the result exceeded my expectations. It will probably take some time until I get the time to build the final product but I want to take the opportunity to share my findings if anyone is planning to go down the same route.

Putting together a complex system is always a matter of tradeoffs. I have made a set of choices, your mileage may vary but know that I made them deliberately based on my specific needs. First of all, I decided to go with all analog controls. It would almost have been easier to go with rotary encoders and a display (easily enable remote control etc.) but that is not how I envision the final product. Another deliberate design decision was to run CamillaDSP and the ADC @ 88.2 kHz but more about that and sound quality in a future post.

I decided to run CamillaDSP on a Raspberry Pi and build around good but cheap and available hardware. I stayed away from USB based capture and output devices and opted for a HiFiBerry DAC+ ADC instead, it is one of the few ADC available as a HAT for the RPi. I initially planned to route input through a switch but I basically only got one analog source these days, my turntable. I use AirPlay a lot for casual listening and I therefor wanted to integrate it as a separate transport.

It might be tempting to add a web based music player managing my collection of ripped CD albums (all in FLAC format) but I don’t want a kitchen sink kind of mess without separation of concerns. I want the preamp to be a preamp and keep the music player on another device (RPi, NAS or whatever). What I would need is a lossless CD-quality transport over IP, preferable Open Source (and not proprietary like AirPlay). Looking for a solution led me to ROC Toolkit.

Another problem with the RPi is the lack of ADC for analog controls like potentiometers and power management. Overlays like gpio-shutdown and gpio-poweroff is great but HiFiBerry is hogging some crucial GPIO pins. Re-configuring the overlays and soldering a couple of pin headers on the HiFiBerry DAC+ ADC card solves the problem and makes it possible to manage power with an external Micro Controller.

I discovered the Raspberry Pi Pico while shopping for an 8 channel ADC for the RPi. The cost was more or less the same so I grabbed a Pico. It has 3 ADC and a bunch of GPIO pins. I decided to make it into a standalone front-end for my analog controls and to use it as the power controller for my RPi. It ended up as another project, meet rpi-sidekick. I tried to keep it generic enough for future reuse in other projects.

I now got pretty much all the bits and pieces needed for my bench tests. CamillaDSP, Shairport Sync and ROC was all configured to run as systemd services and I started to put together a minimal Linux image for the RPi. To get everything going with buildroot felt like too much work so I started out with pi-gen but even stage1 ended up too bloated with NetworkManager, Avahi, D-Bus etc. I therefor turned to Arch Linux ARM and ended up pretty bare metal systemd. I wanted to start-out with just ALSA and no sound server like Pulse of Pipewire to keep boot times fast and things not too complex. I ended up compiling Shairport Sync and ROC without support for Avahi or Pulse. Still a lot of work to be done to optimize it but it was enough proof of concept for me to call it a success.

The functionallity of the preamp was modeled after some of my favorite vintage amps (especially Yamaha CA-800 and Kenwood Model 600) and are:

• A log volume control ranging from -80 to 0 dB attenuation with 12 o'clock @ -20 dB.
• Baxandall tone controls, bass and treble ranging from -10 to 10 dB with individual defeat and two different turnover fq.
• High and low cut filters with individual defeat and two different turnover fq.
• Selectable digital RIAA filters and amplification on analog input (None, Moving Magnet (MM) or Moving Coil (MC))
• Mono filter
• Automatic Adaptive Loudness filter (on or off)
• Mute filter (-20 dB)
• 3 x input transports (ADC, hw:Loopback,1,0 and hw:Loopback,1,1)
• Linkwitz Transform filter (parameters provided as command line arguments to dspreamp)

I have made all my source code available through Codeberg (I left GitHub after the Copilot incident). There are still a lot of information to add in future posts and snippets to be added to the git repository. Especially about ROC streaming from an external music player like MPD. Stay tuned…

DSPreamp @ Codeberg
RPi-Sidekick @ Codeberg

I would also like to take the opportunity to thank Henrik Enquist for sharing CamillaDSP and for patiently answering my questions about its inner workings...

There are some really useful youtube videos out there and I was wondering if anyone here has a channel?

Hello,

This is fully isolated DSC2 DAC project, I'm finished this dac and here is project files for their build. Curently I'm not tested this but my hope somebody from you do it. Note that main buck regulator accept maximum 100V and minimum 5V at the DC imput, and I have set fixed 4.4Vout from the buck. You no need clean DC on DC input since push pull and LT3042 will make clean supply DC voltage for DSC2. Main care must be done to iso push pull reglators because it not accept more than 5.5V!!! You need to wire ferite to 1.2mH on primary and on secondary you need to have 7V, so please do the things carefully right before you put the rest of components on board! Take a look to schematic!

PCB dimension: 90 x 81.5 mm

Ferite is: FEPTN10/6-3E25
dimension: 10,6x5,2x4,4 mm
AL 2250nH
Primary: 1.2mH + 1.2mH, with center tap! Secondary - do it yourself for 7 Vout.

DSC diff current: my choice was 8mA diff, if you need less calculate your resistor values for dsc! My choice was 10k resistors since my i/v frontend accept this value. This is also I think good enought for an transformer based i/v, and I used those 10k values in original dsc2.5.2 with this audio transformer -> https://it.aliexpress.com/item/32810421236.html

Resitor value calculation formula for IdiffMax=+-8mA :
5V / ((0.008A / 32) + (0.008A / 32)) = Rvalue

C_NP and R_NP components if need! Its connected to one of the mount hole pad which will be connected to the case trought metal spacer, and in case you have some noise on iso side you can put resistor and capacior there e.g. 1M + 10nF .

Let see your build, thanks! Enjoy!

Here I will publish a Headphone Amplifier with 6N1P and 6AS7
based on the optimized Morgan Jones circuit with OTL output.
Here is that circuit https://headwizememorial.wordpress.com/wp-content/uploads/2018/03/cmoy5_1a.gif

There will be one circuit for 300 Ohm headphones and one for 32 Ohm.
You are all welcome to follow and discuss 🙂

Here is the 300 Ohm version. It has lower distortion.

Hello everyone, I am a new member of DIYAudio. I like home theater and I want to learn about it. Thank you.

I have a pair of gold cone colored Mark Audio 7.3En drivers for sale. I bought these for a project that I never started. I attached several photos. One of the drivers has a very small crease in the cone. I do not believe this will affect their performance. I tried to take a close up photo to show this. Asking $150 for the pair plus shipping cost.

Hi,
I am selling my Relaixed2 preamp. It is in a case I made with Koa wood for the face. I've downsized and clearing out the closet. Great balanced preamp that can use both RCA and XLR inputs and a XLR for output. I don't have a remote but they are easy to find. $300 plus shipping.

https://www.vaneijndhoven.net/jos/relaixed2/

Hi - Does anyone know what the power consumption of the Amp Camp Amp 1.6 is in watts? In Nelson Pass's notes notes on the F5 he says it consumes 180 watts but I can't find any figure for the Amp Camp Amp. Thanks.

Hey there, I'm Antonio, from Paris, France.

Got into hi-fi a couple years now, and getting into modifying amps and speakers.

Learned a lot on this website!
So I guess is time to share more from my side.

Cheers

I have a Yamaha R8, works fine except for volume and left channel not working.
Turning volume knob has no effect, except for maybe a pop here and there.
Pressing the "Simulated Stereo" button introduces normal behaviour.

Does anyone have an R8 schematic?

"rolibark" mentioned he had an R7 schematic, but the link is broken.

so i would say i became a audio head after purchasing a phillips cd 104 ,my first Cd was Marillion ,script for a jester tears, sure i also had both vinyl and dire straits brothers in arms on cd ,but there was amazing music around so i thought i would post it for some old time memories,
i will also post some of the music that got me into DIY as i needed a subwoofer which happened between 82 & *#,there is more music but these were some favorites
Login to view embedded media Login to view embedded media Login to view embedded media Login to view embedded media Login to view embedded media https://www.youtube.com/watch?v=EZXNr4aa2wk
https://www.youtube.com/watch?v=NbVHiGDMVRI
https://www.youtube.com/watch?v=PedUiJ2TBEg
https://www.youtube.com/watch?v=LnoGts-zT0A
https://www.youtube.com/watch?v=5owM5EitjhQ
https://www.youtube.com/watch?v=wrarS7mLlB0
https://www.youtube.com/watch?v=gE7FK33e0pY
https://www.youtube.com/watch?v=eJ5O6O9jl48
https://www.youtube.com/watch?v=Xl19WyZKCE0
https://www.youtube.com/watch?v=NJA9nQQPqZA
https://www.youtube.com/watch?v=F1RR6vEE7-c
https://www.youtube.com/watch?v=E0uMTJu0ML8
https://www.youtube.com/watch?v=d9Z2CIUjh_0

Happy holidays! Unloading some gear from the archive (aka my storage room).

Audio Note AN-E speakers, mid needs a redone, built up from the official kit

Bastanis dipoles, two pair, includes active subs

Lots of other stuff that isn’t quite free, but come visit and we’ll make a deal. Studio is in Catskill. See what we make here: www.aforara.com

Pickup only (that’s the rub!).

Mouser has a suitable Form A relay, but the amplifier uses both Form A and Form B relays. The Form B is non-stocked with a ridiculous minimum order quantity, so I need to find an alternate supplier. Tried Newark and Digi-Key, but neither had them or their search system was so bad I couldn't find what I needed.
Looking for the appropriate relay in Form B. This is the electrical pinout of the original relays. Both are welded closed and need replacing.

There's a 2016 topic about some people that designed a pcb to use an LT3062 regulator which I found very interesting.

Can anyone update the results over time of those regulators? Are they still working? Were there any problems later on?

Are the regulators reliable and provide all they promise, or they are not?

Thank you for any answers.

Hi guys, working on a vintage MTX Thunder 2300 that came in DOA. Found several bulged caps that apparently shorted out and burned the circuit board pretty badly.
Does anyone have pictures of the underside of the board to see how the traces ran prior to the board burning? If not, a schematic might be helpful. Thanks in advance

Starting a thread to evaluate various op-amps in the output of mainly DIY or legacy DACs.

Here are my recent findings, in case they may be of interest. I've just done listening tests on a bunch of op-amps in the output of my V-DAC, which originally comes with a NE5532. It has a replacement DIP8 socket and also has the 47uF output cap removed. Input is SPDIF via a V-Link, and a V-PSU was used. The V-DAC directly feeds a 2 stage SE tube amp into Mission 761 speakers. Test tracks were Bill Evans album "I Will Say Goodbye" and some Keith Jarrett for piano, Dee Dee Bridgewater "Keeping Tradition" for vocals and Solti Meistersinger (most recent) plus some Steely Dan and modern gospel. Tonality of acoustic instruments was in this case the main consideration.

Top group - judged to have all-round good natural tone including the most realistic piano and vocals
OPA1612
OPA1642
AD8022
AD8066
LT1361
LT1364

Eliminated for various issues
LT1469 - rather thin, very clean
AD8599 - too thin, very clean, excellent high treble
LM6172 - wooden piano sound
LT1057 - bit meh overall

Previously eliminated in a AK4490 DAC
LM4562 - clean but thin
OPA2134 - quite good
OPA2132 - quite good
NE5532 - OK but not special
OPA2228 - nothing special

The top group would need to be re-tested for a winner, but maybe there isn't an overall winner since I enjoyed them all in different ways. For DIP8 you'd need LT1361 or LT1364, the rest needed adapters. They all sounded stable in the V-DAC though they weren't tested with a scope.

Subjective results which apply to directly replacing a NE5532 in a V-DAC output stage, so may not be the same in other contexts. Still, I hope this might be of some use.

Hello everyone,

I've been working on a schematic for a preamp designed specifically for my piezo contact mics, based on the Altoids piezo preamp by Stompville. My goal is to create a compact preamp powered by phantom power, utilizing basic SMD components to minimize soldering and keep costs down. I’ve settled on the TL072 as the op-amp for both buffering and amplification.



I would appreciate any feedback you might have on my design. Here are some specific questions I have:

1) Does the TL072 work well with the used supply and bias voltage?
2) Are the voltage ratings of the capacitors sufficient, particularly for C15 and C18?
3) Are the 100µF capacitors in the power supply section necessary, or can they be omitted? I couldn't find SMD 50V 100µF capacitors in the basic parts category. Or are there other viable replacements?
4) I want to replace the Zener diode D3 with an SMD part. What characteristics should I look for in a replacement?
5) What is the needed wattage rating for the resistors R4 and R5? Is 1/8 W enough or should it be 1/4 W?

Thank you for your help! I’m looking forward to your insights and suggestions.

Best regards,

Benni

Recently, I bought a couple of small cheap Chinese DAC board, with CS8416/CS4344; the boards are intended for a simple low-cost system.

The output pins of the CS4344 are connected to the analog output of the board trough a first order low pass filter, similar to the one proposed in the IC datasheet; beyond this filter, there is a couple of transistor (Q1 and Q2) connected between each signal line (collector) and ground (emitter); I was not able to find where the transistor base is connected.

I can only suppose that this couple of transistors is used as a muting circuit, but I don’t understand the utility.

I tested each board feeding its optical port with the TOSLINK coming out from my CD player, playing Denon Audio Test CD; in the pictures, you can see the DAC board output waveform when reproducing a 0 dBFS sine wave at 315Hz and at 9999Hz.

There are two problems: the distortion in the lower part of the sine and a lot of “dirt” in the 9999Hz sine.

The distortion is caused by the external load of the CS4344 output (probably by the useless output transistor, maybe in inverse conduction?); the waveform at the IC pins is perfect (harmonics level is more than 70dB below the fundamental) when they are isolated from the filter.

The “dirt” on the waveform (I can’t find a better definition) has an amplitude that increases with the frequency of the reproduced sine wave and is completely absent without signal (trace “silence” of the Denon CD); the “dirt” has no components in the audible band (20Hz – 20KHz)

The 3.3V power supply looks clean; the second DAC board I bought behaves in the same way.

The only hypothesis I can do is that the CS4344 internal filters don’t work as they should and the “dirt” I see is the effect of the image frequencies.

Any suggestion regarding the cause of this behaviour and how to eliminate it will be appreciated.

My name is Roy and I'm based in LA. I'm interested in digital crossovers, new/old 3way projects, Purifi and Bliesma drivers. Just getting my toes wet so I have lots to learn from everyone. Thank you in advance for your advice and patience for my noob questions.
Roy

Hello, while trying to take quasi-anechoic for some of my test speakers for a variety of drivers, I noticed that non of them exhibit, the usual behavior, of sharp SPL drop from the woofer around the port tuning frequency. Also, when measuring the impedance with REW and a DIY jig, there aren't two separate and define spikes of impedance (the middle of which is usually the port tuning frequency). The measurements show relative agreement with models made with WinISD show I suspect it's something with my designs.

How should I utilize drivers like this in vented enclosures? The ND90 supposedly should be able to provide good and linear results, but the other two either give a huge output spike if the tuning frequency is near the Fs or the response ripples near the roll off.

Driver's I've used:
ND90 8ohm
TEBM35C10-4
Aliexperss 3inch T/S parameters acquired with manual measurements.

(measurements not baffle diffraction corrected)

Hi guy newbie here, I have some sony deep bass speakers that I fitted with a fenton intigrated amp from a spb8 400w, thinking that it would be enough for family karaoke parties, but sadly it doesnt preform well, the interphase is great it can read mp3 on both sd or usb, it has bluetooth to connect a phone or laptop, has seperate volume and echo for twin mics a simple tone control with seperate volume for music, but not a master volume control.
I also have a compact ish samson 260 w servo studio amp which runs the speakers beautifully, my plan is to steal a signal from the small amp to feed the samson input.
The fenton amp uses 4x tip41c transistors npn on 4 tiny HS. I'm guessing they use 1for music and number 2 for the mic feeding the left speaker and similar to feed right speaker, even though the heatsinks are small they do interfere with the tweeter horns and would be better shortened to be 'nice'. My question is should I pull the signal from the 5551 and 5401 driver transistors or reduce the collector voltage of the tip41c down to an acceptable level to feed the samson preamp. Sorry for the essay hope you are still awake !!
Thanks guys.

Good day guys, I have an Hifonic Brutus Class-D to rebuild Power supply…I was thinking to use the 3205 Mosfets but my local supplier is out of those, what are the next best mosfet and gate resistor I can use comfortable drop in?

As a quick distraction from the everyday I decided to jump down the guitar amp rabbit hole again. I've been looking into "intentional" distortion, and something doesn't make sense to me. In higher end amplifiers, distortion is usually created by cascading multiple gain stages, cumulatively driving the last tube of the preamp, and then into the power section. Couldn't that same effect be created by using an op amp circuit with sufficient gain pumped into that last tube stage? For that matter, couldn't some of that distortion also be supplanted by diodes in the same circuit in order to account for the lack of it in prior gain stages? Or would that not matter since you would be driving that tube with so much gain anyway?... Or is this another case of "you missed this..."?

These days I found a seemingly flawless Phillips subwoofer (from a HTD5000 home theater) on the street, in a spot meant for trash, its only issue was that someone ripped off its wires.

I took it home and soldered new wires, it works, but sounded lame, despite the fact it looks perfectly intact.

It's speaker is an 8 inch Eastech sub, FSB52A680-8300, a driver that exists for sale only here in Brazil (used ones only) and that doesn't exist even on Eastech's site itself, nor any other database.

This is it:



It's visually similar to this other 8 inch sub from Eastech, same design, basket shape etc, except for the magnet, mine looks like is has only 60% of the diameter of this one here: https://www.eastech.com/standard/asdsd4026-0301. Plus, according to the site, its surround is supposed to be rubber, mine is foam (a good quality one, but foam).

Even its Fs and Re are similar.

The only problem is that, after I measured its TS parameters using a setup I already used before, I've found its BL to be only 4.67 N/A, causing it to have a large Qts of 0.896.

I've used this setup several times, and it never seemed to give nonsense results, I rechecked my calculations and everything thrice, everything seemed correct, but decided to do a second test:

I've put a thin copper wire attached on the frame of the speaker, coming up above the cone and making a hook shape above the surround, in such a way its tip lightly touched the cone, when it's at rest, to mark its resting position (when lying on a surface, with its cone pointed up).

Then I fed it a DC current and checked how much weight I needed to pile over it (only non-magnetic materials, of course) until it returned to its resting position. When that happens, the coil force and the weight force are canceling each other out, and the surround and spider are keeping it at the resting position again.

My measurement came to the result of 4.79 N/A, strikingly close to one calculated based on its max impedance, Re and side frequencies.

So I've accepted that, whatever the reason, it has a very low BL.

My question is: why? How?

Honestly I don't think this could be the result of aging or demagnetization.

Perhaps, has it always been like that?

The smaller magnet would make sense with this idea. Eastech itself has a few subs with similar Qts, but much higher Fs. None has an Fs similar to 40 Hz and such a high Qts.

But that would mean this sub was never properly tuned.

With the TS parameters I'm seeing now it's completely improper for any vented design, leave alone its original enclosure, which is why it was sounding horrible.

The TS parameters I got were:

Vas=35.896129906 L
Cms=0.547857247922 mm/N
Mms=33.7729816147 g
Qes=1.04372168889
Qms=6.35603786481
Qts=0.896506775221
Re=2.9 Ohm
Fs=37 Hz

on an Onkyo Dx-1400, and I am sure others, there are two connectors for wires to the CD mechanism (actually 4) that are 8 and 9 pins and go from the board to the laser assembly. Does anyone know exactly what these connectors are so that I can order a new plug. single row, 2mm pitch, pins on the board and crimped sockets on the wire end.

Hi gang.
A guy in the German Visaton Forum did a mod to the Visaton BG20 that is worth sharing here.
Maybe it has been covered but I did not find it with the search engine.
The basic mods like additional magnet on the back, basket damping and felt rings in the center of the voice coil suppose to benefit the BG20 allot but
this mod seems to make the biggest upgrade to the unit:
Applying Dekalin a visco elastic sticky sealing paste onto the ridges of the surround exhibit the following measured results.
First photo is the stock unit
Second with only the inner ridge treated
Third with two ridges treated

Hello all. Can some H2 units be modded to a 3-way active tone control with gain and without losing the H2 flavour?

PCB (1) will be less than 10$ US each + envelope +shipping (to be confirmed based on quantity). Price will decrease if the numbers of pcb increases. Therefore this is not commercial Diy...

Please write your name here and the quantity from the latest list in the thread.
1)
...

Hundreds of pcbs have been already delivered to Diy builders.

See more details about the USSA-5 here:

USSA-5 Build with Review


------------- added information ---------

USSA is a family of 20-25 Wrms (8 ohms) class A amplifiers depending on PSU and bias current.
For 4 ohms load it will give still about close to 20Wrms in class A (Square law effect) and up to 45-50 Wrms in class AB.

Design philosophy:

• Current feedback type thus almost constant feedback factor amongst all the audio band.
• only 2 stages (also with buffer stage for versions 3 to 5)
• low/medium feedback factor (< 35db)
• medium damping factor (25 to 70 for 8 ohms load at 100 Hz), depending on version
• Square law effect maximizing class A for mosfet output versions (very low source resistor)
• push-pull that allows to switch into class AB if maximum of class A is reached
• THD is dominant 2nd and 3rd harmonics
• Audio grade transistors only and operated in their more linear region
• Soft clipping behaviour
• main target is big soundstage, sound big (not thin) even at lower level, articulated bass, natural tonal balance (not artificially over bright), no extra sibilance and overall smoothness while being lively.

Pcb features:

• output transistors optimally positioned for better heat distribution on heatsink;
• carefull layout using ground plane, ground return scheme, reduced cross coupling of signals and proper feedback point
• 2oz density copper trace
• 2mm pcb thickness
• gold immersion exposed traces
• pcb compatible with either USSA-3, 3.1, 3.2 or USSA-5 , 5.1 , 5.2
• pcb almost compatible with USSA3B or 3.xB and USSA5B or 5.xB (reverse output transistors pin out)
• LATERAL fet ouputs for initial versions (except versions 7 and 8)
• BJT ouput for B versions

See post # 346 for schematics of USSA5, USSA5.1 and USSA5B: USSA-5 PCB GB

For USSA3B and USSA3.1 see this thread:
USSA-3B new Version based on USSA-3
USSA3.2B: jfet input, using quad matched available mosfet drivers. Using power bjt as output.

Summary comparison table of USSA-X variations:

notes:
1) versions 7 and 8 are twin turbo class AB versions : +-/ 42VDC and double output. They are prototypes using a pcb meant for single output device thus needs wires to connect two pairs. There is no build manual and not supported for Diy. Special request can be submitted by personal message for USSA-8 for more experienced builders.
2) as a general note, for about the same damping factor, bass is tighter and snappy for mosfet output and less tight but maybe stronger for bjt output
3) damping factor may vary based on input stage current.
4) obviously, more details can be less forviving for bad recordings or low grade input source.
5) all class A designs have a more relaxed sound than the class AB in the table above. If high power is not mandatory, I personally recommend class A for better sound.

Documentation:
detailed manual including pictures at different steps and intermediate testing procedure at different phases of assembly to ensure fully working board at end of assembly.

Test equipment needed:

• 2 x standard multimeters (precision 1mv) ( mandatory)
• intelligent phone/pad sound generator application (optional)
• 8-10 ohms 20W power resistor (optional)

Warnings:

• If you are looking for a high power very bright sound this amp is not for you.
• If you are listening mainly hard rock/metal music at high sound level this amp may not be for you. However, I mainly listen progressive rock at medium/high level and it sounds fine to me. Still my main amplifier.
• if you want very tight /dry bass ( as opposed to articulated emotional big bass ) than this amp is not for you.
• if you are not ready to manage the heat generated by class A than this amp is not for you.

Group buy conditions:
1) partial manual including BOM is provided (only adjustment instructions are missing) since from my estimation roughly only 10-15% of pcb sold are really used for a real build within one year...
2) once pcb are paid, I provide the complete manual including adjustment instructions.
3) once all payments received, I order the pcb from manufacturer.
4) I ship the pcb to your provided address.

Update on 2021/08/17:
Unfortunately the darlington bjt drivers used on USSA-5.1, 5B, 3.1 and 3B are now obsolete. For that reason. An alternate part for the driver is used. Thus this is a new version 5.2. Great sounding ! See post #701 and 702 for more details.

Fab

I made a batch of MIC5156 based LDO supplies, parts cost is 15 euro selling these for €27.50 for my troubles in assembly and testing, ex shipping. Will ship worldwide at cost.

I have 6 available that arent spoken for, Reichelt will deliver the coolers sometime this week, and then its an afternoon of soldering to get them ready to ship.

Photo attached of my previous batch.

Fully tested and assembled, €27.50 or about 30USD.

Boards are good for 2.5A provided the winding can deliver that much current as the 2x 15mF 10VDC has quite an ugly current waveform.

Once these run out, i will do another batch either as a parts kit or assembled of Revision 2. its the same board but more through hole components.

Hoping for some repair help.

I have recently obtained an Ashdown Rootmaster MAG420 1x15 bass combo for free, as a repair project. The combo is in excellent condition for being probably 10 years old, very clean, and with no missing knobs or exterior damage. But the guy I got it from told me that his bass player had plugged it in one day to play and got a bang and blue flash. He obviously hadn't plugged it in since.

Taking a look inside, I see that the amp uses an Anaview ALC0300-1300 power supply and amp module, datasheet attached. From what I can see online, these were once well-regarded, but Anaview and its successors have been swallowed up by acquisitions, and no support or replacements are available.

I inspected the interior of the amp very closely for signs of damage from the flash and bang that was mentioned, he had indicated it was near the mains input, but other than the main fuse being blown I could see no damage. I am not an electronics engineer, but I have done some basic repairs, soldering etc. although not on amps and power supplies like this. But I tested for short circuits on the main inputs and outputs of the PCB, and even PAT tested the whole amp, it passed no problem. The fuse on the amp/power supply PCB was not blown. So I wondered if the flash had just been a bit of an extra surge blowing the main fuse.

So I bit the bullet, put a new fuse in, plugged it in and flipped the switch. Sure enough, huge bang and flash, the main fuse blew, the breaker of the socket blew, and then I saw damage! It was at the corner of the PCB where the flash had been. in addition to some pics of the amp interior generally, and some closeups of the damaged area, I put a pic of this damage below, after I had cleaned it a little with a brass brush. I'm not 100% sure but fairly positive it did not arc from this point to the ground connection point which is surprisingly close, as you can see in some of the pics. But I still can't see any clearly damaged components, just the area of the board. I noticed that the one solder point of the large capacitor nearest the damaged area looks a little stressed. Could it be that this cap is bad? How would I test for this? I did test and it is not shorted.

Can anyone give me some tips on what the issue may be, or what to test next? Or does someone have a working ALC0300-1300 module in the UK that they are looking to sell? I would really really love to get this combo going, as it's in great nick otherwise, and has all the features I am looking for. I am really hoping to repair this myself, although I suppose I could ship it to a repair house, but that could cost more than the amp is worth...

Currently i'm a lowly Spotify premium user streaming via MiniDSP flex 8 bluetooth through my Android phone. In an effort to possibly improve things, I'm waiting on a WiiM mini streamer to test out the limits of Apple Music, which i understand can stream lossless over Airplay 2? In order to achieve lossless streaming may I control Apple music through an Android phone or must I have an apple device to actually receive/control (mac mini /ipad/iphone) Lossless?

I question if any of this makes a difference vs. my current stream via LDAC bluetooth? Is a cheap PC tethered via USB to the MiniDSP Flex 8 streaming Spotify premium inferior vs. Apple Music Lossless via a WiiM streamer? I don't know, but hoping someone with more experience can share their experience. mahalo.

Hi guys 70 yr old newby here, I'm a rock music lover and have always been into audio stuff I love making and modding stuff and like to learn cheers !

Got a tougher one. I have a Nikko Alpha III that I cant set the idle current on. I just installed some used Exicon mosfets. A bit of history. I bought this off ebay along with a Nikko Beta 30. The beta 30 was completely recapped along with some new transistors in the power supply and installed some LM4562 opamps and it sounds great. The Alpha III was doing very well and had bought all the hardware needed for a complete recap. Bad storm hits and pulled my power lines loose enough I had a lost neutral condition and my power protector got a 160v surge, uh yeah. Alpha III smoked and the J49 mosfets took a dive. The 134's survived. I started working on it with another fellow tech and I replaced the trannys on the complimentary differential board which were 2sa872 and 2sc1775. I did hfe matching of the transistors on the left channel only. Once completed it came out of protection but I can not adjust the offset or idling. Following the manual when adjusting the offset and using a shorting pin on the direct input jacks the lowest I can get is 1.62 vdc, left channel and the right side I can adjust right on the nose. Idling adjust ment is stuck on .2mv and no adjusment no matter how much I turn the pot both sides. Funny thing is if I connect the DMM to the pins it reads .2mv with no power.
I know its alot but it helps give you some insight. I have attached the manual. Any suggestions would be greatly appreciated
Phil

Hello not sure if this is the right forum I do apologize, I know the title is a bit weird but I will try my best to explain it. I have been using this tone control from Aiyima ( I know tone control is not very popular here) and I happen to like the sound of it very much, I swapped out the ne5532 op amps for some OPA2134's and it sounds very good. The issue is that this preamp is mounted in the chassis of an amp I built and I made some extensions (roughly max length is 12in) for the potentiometers like this for example so I could mount the pots to the front plate. In doing so I encounter a lot of buzzing noise that is audible when ears are very close to the tweeters on my speakers. I used this 6 conductor twisted pair shieled wire to extend the pots and tied the shield to common which did decrease the amount of noise greatly but wondering what else I can do to get rid of the rest of the buzzing noise. The does also persist when the preamp board is not in the chassis aswell. Any help would be greatly appreciated.